The German patent DE 44 29 498 C 1 discloses a plug-in coupling for connecting a fluid pipeline with a pipe. The plug-in coupling is provided at an angled piece of pipe, whose end can be connected with the fluid pipeline. The end of the fluid pipeline can be stuck together with the pipe and connected to the pipe via holding arms. An anti-twist protection holds the pipe in a defined angle position, so that the fluid pipeline and the pipe can be connected under a fixed angle of rotation in different relative position of rotation to each other. Separating the fluid pipeline and the pipe can be achieved by pressing together an oval ring, which surrounds the plug-in coupling. Due to the pressing together, retaining ribs disengage latches, therefore the fluid pipeline and the pipe can be separated.
The German patent DE 199 46 260 C 1 shows a quick coupling for tubes or pipes with a clutch housing. A plug nipple and a locking element are proposed, wherein locking and releasing of the locking occurs from one side of the clutch housing. The access to the quick coupling happens from the outside and a protection of pollution of the inner quick coupling is achieved.
The German patent application DE 34 40 783 A1 reveals a pipe coupler with a coupling nipple, surrounding by an abutment shoulder. The coupling nipple can be inserted into a coupling sleeve. A locking tappet engages in a closing position with two almost parallel legs sideways at the abutment shoulder. The legs attach in the area of their ends wedge-like arranged guide surfaces. The guide surfaces are arrange like that, that they impinge the weir gate into the direction of the closing position.
The U.S. Pat. No. 5,607,192 reveals a pipe connection for a water treatment system. The pipe connection contains an adapter from the water treatment system and a positioning means, which attaches a connecting means for the pipe at the water treatment system. The positioning means mounts the pipe with a C-shaped retaining section.
The European patent EP 1 559 944 B1 reveals a plug-in coupling for connecting a fluid pipeline with a pipe, as well. The end section of the pipe can be stuck together with the end section of the fluid pipeline, wherein elastic holding arms of an expandable part of a coupling ring make the fluid pipeline and the pipe stay connected. The part of the coupling ring has ratchet sections, spread over a sector of peripheral angle, which slip away and lock below the retaining rip when clutched in through the retaining rip by stretching the part of the coupling. By pressing manually the ends of its big axis, the part of the coupling can be stretchable, as well as the ratchet sections, for releasing the coupling. For safety reasons, to prevent, that the plug-in coupling can be released manually, the part of the coupling has at least three ratchet sections and the sector of peripheral angle is larger than 180°. If it is tried manually to deform the part of the coupling to release the coupling, at least one ratchet section will be engaged below the retaining rip.
The above described prior art does not allow that the plug-in connection is released between the two connected pipes in an easy manual way. In addition, the connection of the pipes is normally arranged in the outside section of the automobile and exposed to dirt. Dirt in the area of the connection of the two pipes complicates the release of the plug-in connection.